The present invention relates to a method of manufacturing a photoconductive film type light receiving element for converting data on ordinary clerical documents into electrical signals in time-series and a product produced by this method.
More particularly, the invention relates to a method of manufacturing a film type light receiving element in which a photoconductive non-crystalline film is formed, for instance, by vacuum evaporation on a flat and smooth insulating substrate on which belt-shaped electrodes are arranged in a desired density and in which an optically transmissive electrode is formed on predetermined parts of the belt-shaped electrodes. A film of Au or the like is used for each of the belt-shaped electrodes, an Se-As-Te film is used for the photoconductive non-crystalline film, and an InSn oxide film (hereinafter referred to as "an ITO film") or an Sn oxide film which is obtained by sputtering under an argon pressure of 3.times.10.sup.-3 to 4.times.10.sup.-3 Torr and an oxygen pressure of 1.8.times.10.sup.-4 to 3.times.10.sup.-4 Torr with a compound In.sub.2 O.sub.3 - SnO.sub.2 or SnO.sub.2 as a target.
FIG. 1 is a sectional view showing the structure of a conventional film type light receiving element. Belt-shaped electrodes 2, a photoconductive film 3 and an optically transmissive electrode 4 are formed on a flat and smooth substrate 1 in the stated order. For instance, the substrate 1 is made of a highly insulative material such as quartz glass or Vycor.TM. brand glass, the belt-shaped electrodes are formed of an Au film, the photoconductive film 3 is an Se-As-Te film or a CdSe film, and the optically transmissive electrode 4 is an InSn oxide film or an Sn oxide film.
In FIG. 2, the curve I indicates specific resistance .rho. with oxygen partial pressure P.sub.o in a sputtering atmosphere for the case where an ITO film is formed on a glass substrate with a magnetron type sputtering device using an ITO target.
By forming on a flat and smooth substrate of Pyrex.TM. glass the belt-shaped electrodes, i.e. the Au films 2, the photoconductive film, i.e. the Se-As-Te film 3, and the optically transmissive electrode, i.e. the SnO.sub.2 film 4 in the stated order, a light receiving element having a structure as shown in FIG. 1 is obtained.
Heretofore, the electrical conductivity and the transmissively of the optical transmissive electrode have been considered as important factors. It has previously been considered impossible to increase the electric current ratio for light and dark intensities which is the most important factor of the photoelectric conversion element.
Accordingly, an object of the invention is to provide a method of manufacturing a film type light receiving element in which the above-described difficulty accompanying the conventional method is eliminated and the electric current ratio for light and dark intensities is increased.